Changes in signal transduction and disease Original Scenario-Based Download PDF

Questions

1. 1.

   A deep-sea research expedition investigates an anomalous population of bioluminescent cnidarians exhibiting constant, unregulated light emission even in complete isolation from environmental triggers. Molecular analysis reveals a loss-of-function mutation in the catalytic site responsible for GTP hydrolysis within the G-alpha subunit regulating luciferase activation. Based on the mechanisms of signal transduction disruptions in disease states, what is the direct cellular consequence of this molecular alteration?

   • A) The G-alpha subunit remains persistently bound to GTP, continuously stimulating its downstream effector enzyme without needing upstream receptor reactivation.
   • B) The G-alpha subunit fails to exchange GDP for GTP, locking the heterotrimeric complex in an inactive state and abolishing target enzyme activity.
   • C) Intracellular phosphodiesterases are irreversibly inhibited, preventing the synthesis of cyclic adenosine monophosphate (cAMP) second messengers.
   • D) The transmembrane receptor undergoes continuous endocytosis and degradation, completely desensitizing the cell to intracellular secondary messengers.